TW202301024A - Method and system of cleaning surface of reticle - Google Patents

Abstract

A method of cleaning a surface of a reticle includes retrieving a reticle from a reticle library and transferring the reticle to a first exposure device. The surface of the reticle is cleaned in the first exposure device by irradiating the surface of the reticle with an extreme ultraviolet (EUV) radiation for a predetermined irradiation time. After the cleaning, the reticle is transferred to a second exposure device for lithography operation.

Description

Reduce Contaminant Breakdown Effects on Masking Defects

During integrated circuit (IC) design, multiple patterns of the IC are generated on the substrate for different steps of the IC process. The plurality of layout patterns may be generated by projecting (eg, imaging) a plurality of layout patterns of a mask onto a photoresist layer of the wafer. The lithography process transfers the layout patterns of the mask to the photoresist layer of the wafer such that etching, implantation or other steps are only applied to predefined areas of the wafer. Generally, reticles (eg, masks) are stored in a reticle library under vacuum conditions when the reticles are not in use.

The following disclosure provides many different embodiments or examples for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. Of course, these are just examples and not intended to limit the present disclosure. For example, in the illustration, a first feature is formed on or over a second feature, which may include embodiments where the first feature is formed in direct contact with the second feature, which may also include that additional features may be formed on the second feature. An embodiment between a feature and a second feature such that the first feature may not be in direct contact with the second feature. In addition, this disclosure may repeat reference numerals and/or text in various instances. This repetition is for the purposes of brevity and clarity, and is not intended, in itself, to specify a relationship between the various embodiments and/or architectures discussed.

Furthermore, spatial relative terms may be used here, such as "beneath", "below", "lower", "above", "upper", etc. etc., to facilitate the description of the relationship between one element or a feature and another (other) elements or features as shown in the drawings. These spatially relative terms are intended to cover different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be positioned in different ways (eg, rotated 90 degrees or at other orientations), and the spatially relative descriptions used herein should likewise be construed accordingly. Furthermore, the term "being made of" can be interpreted as "comprising" or "consisting of". In this disclosure, the term "one of A, B, and C" is interpreted as "A, B, and/or C" (that is, A, B, C, A and B, A and C, B and C, or A, B, and/or C) B and C), and unless otherwise stated, are not to be read as one element from A, one element from B, and one element from C.

In some embodiments, reticles are stored in a reticle library, and the reticle library is maintained under vacuum conditions to avoid deposition of particles and hydrocarbon contaminants ( Hydrocarbon contamination). However, when the photomask is used during the lithography process, particle and hydrocarbon contamination may build up on the photomask. Particle and hydrocarbon contamination may compromise critical dimension (CD) uniformity in patterns produced on the photoresist layer of the wafer. In some embodiments, after the reticle is retrieved from the reticle library, the surface of the reticle is cleaned of particles and hydrocarbon contamination with a solvent. In some embodiments, the surface of the reticle is cleaned of particles and hydrocarbon contaminants with a solvent prior to storing the reticle in the reticle library. Solvent cleaning the reticle may introduce additional particles into the reticle library if the reticle is cleaned prior to storage. If the reticle is cleaned after it has been retrieved from the reticle library, cleaning the reticle with a solvent may introduce additional particles into the exposure device of the lithography system. In addition, cleaning the photomask with solvents may cause long delays in the lithography process. Thus, in some embodiments, the reticle is cleaned offline. Retrieve the reticle from the reticle library, clean the retrieved reticle, and store the reticle in the reticle library again.

When a mask is retrieved from a mask library and the mask is used in the lithography process, particles and/or hydrocarbon contamination may accumulate on the mask, which may degrade the mask and may cause The critical dimension (CD) of the wafer is not uniform. Therefore, it is desirable to be able to clean the photomask before performing the lithography process. In some embodiments, the lithography system includes two exposure devices. One of the two exposure devices is used to project a mask on the photoresist layer of the wafer to pattern the wafer. The other of the two exposure devices has a separate radiation source (such as an extreme ultraviolet (EUV) radiation source), and the other of the two exposure devices is used for irradiating the surface layer of the mask. In some embodiments, the energy of the irradiation is used to break down the layer of particulate or hydrocarbon contamination deposited on the surface layer of the reticle. In addition, the more the surface layer of the reticle is exposed to radiation, the more the particle or hydrocarbon contamination layer breaks down. In some embodiments, the photomask is a reflective reticle. Irradiating the surface layer of the photomask for a long time will not only delay the lithography process, but also may damage the layers of the photomask. Damage to the layers of the reticle, such as the reflective layer of the reflective reticle, may damage critical dimension (CD) uniformity. Accordingly, it is desirable to irradiate the surface layer of the reticle to reduce or eliminate the effect of particulate and hydrocarbon contamination on the surface layer of the reticle without damaging the structure (eg, reflective structure) of the reticle. Therefore, it is desirable to irradiate the surface layer of the reticle before damaging the reticle structure to obtain the best improvement in critical dimension uniformity (CDU).

FIG. 1 is a process flow 150 for producing a photoresist pattern on a semiconductor substrate. In some embodiments, the process flow 150 is performed by the control system 800 of FIG. 8 and/or the computer system 1000 of FIGS. 10A-10B . In photoresist coating operation 102 , a photoresist layer of photoresist material is disposed (eg, coated) on a top surface of a substrate (eg, a workpiece wafer). As shown in FIG. 5B , the photoresist layer 15 is disposed on the semiconductor substrate 10 . A post application bake (PAB) is performed in a post application bake (PAB) operation 104, and the semiconductor substrate 10 including the photoresist layer 15 is baked to drive out the solvent in the photoresist material and cure A photoresist layer 15 on top of the semiconductor substrate 10 .

In the embodiments of the present disclosure, the terms "mask", "photomask" and "reticle" may be used interchangeably. In addition, the terms "resist" and "photo resist" can be used interchangeably. In mask extraction operation 105, a mask is extracted from a mask library. The mask extraction operation 105 is described in more detail in the description of FIG. 2 . The captured reticle is loaded into the exposure device by mask load and exposure operation 108 , depicted in FIG. 4 . The mask loading and exposing operation 108 also projects the mask onto the photoresist layer 15 of the semiconductor substrate 10 using actinic radiation from a radiation source. In some embodiments, the layout pattern on the mask is projected onto the photoresist layer 15 by means of extreme ultraviolet (EUV) radiation from an extreme ultraviolet (EUV) light source to generate the pattern in the photoresist layer 15 on the semiconductor substrate 10. photoresist pattern. In a post exposure bake (PEB) operation 110, a post exposure bake (PEB) is performed on the wafer, wherein after exposure to actinic radiation and prior to development in a development operation 112, further baking photoresist layer. By applying a developer solution to the photoresist layer 15, the photoresist material of the photoresist layer is developed. For a positive tone photoresist material, in a developing operation 112 , the exposed areas are developed by applying a developer solution, then the developed areas are removed and a photoresist pattern of the photoresist layer 15 is produced in the remaining areas. For negative tone photoresist materials, in developing operation 112 , the unexposed areas are developed by applying a developer solution, then the developed areas are removed and the remaining areas generate a photoresist pattern of the photoresist layer 15 . The mask is depicted in Figure 5A.

FIG. 2 shows a rapid exchange device (RED) 200 for transferring reticles between different locations. The rapid exchange device (RED) 200 transfers the reticle between the reticle library 202 , the first exposure unit 212 and the second exposure unit 214 . Rapid exchange device (RED) 200 includes a robotic device 206 having a robotic arm. The robot arm includes a first movable section 204 and a second movable section 208 . The second movable section 208 rotates about the first pivot point 205 . The first movable section 204 rotates around a second pivot point (not shown) in the robot device 206 , and the first movable section 204 also moves the first pivot point and the second movable section. The robot device 206 can rotate the first movable section 204 and the second movable section 208 around respective pivot points to extend the robot arm to the mask library 202 , the first exposure device 212 or the second exposure device 214 . In some embodiments, the robotic apparatus 206, the reticle library 202, the first exposure apparatus 212, and the second exposure apparatus 214 are maintained in a vacuum environment.

The rapid exchange device (RED) 200 also includes a rapid exchange device (RED) controller 240, and the rapid exchange device (RED) controller 240 is coupled to the mask library 202, the robot device 206, the first exposure device 212 and the second exposure device 214. In some embodiments, a rapid exchange device (RED) controller 240 commands the robotic device 206 to retrieve a mask from the mask library 202 and load the mask into the first exposure device 212 or the second exposure device 214 . In some embodiments, the rapid exchange device (RED) controller 240 commands the robotic device 206 to retrieve the reticle from the first exposure device 212 or the second exposure device 214 and load the reticle to the other exposure device. In some embodiments, rapid exchange device (RED) controller 240 commands reticle library 202 to release one of the reticles to be retrieved. In some embodiments, a rapid exchange device (RED) controller 240 commands the robotic device 206 to load a mask on the mask table of the first exposure device 212 or the second exposure device 214 . The first exposure device 212 and the second exposure device 214 are depicted in Fig. 4, Fig. 5B and Fig. 7A.

FIG. 3 is a process flow 300 for producing a photoresist pattern on a semiconductor substrate according to some embodiments of the present disclosure. The process flow 300 includes the photoresist coating operation 102 , the post application bake (PAB) operation 104 , the post exposure bake (PEB) operation 110 and the development operation 112 of the process flow 150 of FIG. 1 . Additionally, the process flow 300 includes a mask capture operation 105 performed by the rapid exchange device (RED) 200 of FIG. 2 . During the mask capture operation 105 , the RED controller 240 of FIG. 2 commands the robot 206 and the mask library 202 . In response to a command from a rapid exchange device (RED) controller 240, the mask library 202 releases the mask and the robotic arm of the robotic device 206 extends into the mask library 202 to retrieve the released mask. The process flow 300 also includes a mask load and clean operation 106 . During the mask load and clean operation 106 , the rapid exchange device (RED) controller 240 commands the robotic device 206 to load the released reticle in the first exposure device 212 . In addition, after the reticle is loaded in the first exposure device 212, the rapid exchange device (RED) controller 240 commands the radiation source (such as an extreme ultraviolet (EUV) light source) of the first exposure device 212 to emit radiation from the radiation source at a predetermined The amount of time to irradiate the surface of the reticle to clean the surface of the reticle. In some embodiments, the radiation source is an extreme ultraviolet (EUV) light source or other light source having a suitable wavelength that breaks down hydrocarbon contaminant layers and particles. In some embodiments, the surface of the reticle is a surface region of the reticle that reflects radiation into the reticle. In some embodiments, as at least part of the cleaning operation and irradiating the surface of the reticle, the layout pattern of the reticle is projected on a dummy wafer. And, in the mask loading (mask load) and exposure operation 108, the reticle loaded in the first exposure device 212 is transferred to the second exposure device 214, and the radiation source of the second exposure device 214 changes the layout of the reticle The pattern is projected onto a photoresist layer of the substrate (eg, photoresist layer 15 of substrate 10 of FIG. 5B ) to generate a photoresist pattern.

FIG. 4 is a schematic diagram of an exposure apparatus 400 for producing photoresist patterns on a wafer. Exposure apparatus 400 , identical to second exposure apparatus 214 , is shown exposing a photoresist-coated substrate with a patterned beam of radiation 29 from radiation source 100 , such as an extreme ultraviolet (EUV) radiation source. In some embodiments, the exposure device 400 is an integrated circuit lithography tool, such as a stepper, a scanner, a step and scan system, a direct write system, etc. system), use contact and/or proximity mask (contact and/or proximity mask) devices, etc., integrated circuit lithography tools, for example, provide one or more optical elements 205a, 205b of the optical system, and use extreme ultraviolet (EUV ) beam of optical radiation to illuminate a patterned optical element (e.g., a mask, such as reflective mask 205c) to produce a patterned beam of optical system and one or more reduction projection optical elements 205d, 205e, the optical system It is used to project the patterned light beam onto the target semiconductor substrate 210 . The target semiconductor substrate 210 corresponds to the semiconductor substrate of FIG. 5B. In some embodiments, a photoresist layer consistent with the photoresist layer 15 of FIG. 5B is disposed on the target semiconductor substrate 210 . A mechanical assembly (not shown) may be provided to create controlled relative motion between the target semiconductor substrate 210 and the patterned optical element (eg, reflective mask 205c). By controlled relative motion, different dice of the substrate are patterned. In some embodiments, the exposure device 400 is an extreme ultraviolet lithography (EUV lithography, EUVL) exposure device. As further shown, the extreme ultraviolet lithography (EUVL) exposure apparatus of FIG. 4 further includes an extreme ultraviolet (EUV) radiation source 100 to irradiate a target semiconductor substrate 210 . In some embodiments, since gas molecules absorb EUV light, the lithography system used for EUV lithographic patterning is in a vacuum environment to avoid loss of EUV intensity. In some embodiments, the pressure in the exposure device 400 is sensed by a pressure sensor 408 in the exposure device 400 , and the pressure in the exposure device 400 is controlled by a vacuum pressure controller 406 coupled to the exposure device 400 . In some embodiments, reflective mask 205c is identical to reticle 80 described below with respect to FIG. 5A. In some embodiments, the vacuum pressure controller 406 is included in the rapid exchange device (RED) controller 240 of FIG. 2 .

In some embodiments, the target semiconductor substrate 210 is a dummy wafer and the exposure device 400 is identical to the first exposure device 212 . As described with respect to FIG. 2 , the reticle retrieved from the reticle library 200 is loaded into the exposure device 400 as the reflective mask 205c. In some embodiments, the semiconductor substrate 210 of FIG. 4 is a dummy wafer and irradiates the reflective mask 205c with radiation from the radiation source 100 for a predetermined amount of time to clean particles and/or hydrocarbons on the surface of the mask. pollutants.

5A-5B are cross-sectional views of the reflective mask structure 80 and the projection of the reflective mask structure 80 on the semiconductor device 34 in the exposure apparatus. FIG. 5A shows a cross-sectional view 500 of a reflective mask structure 80 (eg, a reflective mask). As mentioned above, the terms "mask", "photomask", and "reticle" are used interchangeably. The reflective mask structure 80 is consistent with the reflective mask 205c of FIG. 4, and the reflective mask structure 80 is used in the exposure structure 400 of FIG. As shown in FIG. 5A, the reflective mask structure 80 includes a substrate 30 having a suitable structure, such as low temperature expansion material or fused silica. In various examples, the material includes titanium dioxide (TiO ₂ ) doped with silicon dioxide (SiO ₂ ) or other suitable material with low temperature expansion properties. The mask includes a plurality of reflective layers (ML) 35 deposited on a substrate 30 . A plurality of reflective layers (ML) 35 includes a plurality of film pairs (film 37 and film 39), such as molybdenum-silicon (molybdenum-silicon, Mo/Si) film pairs (for example, in each film pair, on the silicon layer or molybdenum layer below). Alternatively, the plurality of reflective layers (ML) 35 may include molybdenum-beryllium (Mo/Be) thin film pairs, or other suitable materials that may be configured to be highly reflective to extreme ultraviolet (EUV) light. The mask may also include a protective cover layer 40 such as ruthenium (Ru) disposed on the reflective layer (ML). The mask also includes an absorber layer 45 deposited on the reflective layer (ML), such as a tantalum boron nitride (TaBN) layer. The absorber layer 45 is patterned to define a layout pattern 55 for the layers of the integrated circuit. Alternatively, other reflective layers may be deposited on the reflective layer (ML) and patterned to define the layers of the integrated circuit, forming an extreme ultraviolet (EUV) phase shift mask.

Figure 5B illustrates exposing a photoresist layer disposed on a semiconductor device to radiation. FIG. 5B is a simplified diagram consistent with FIG. 4 for projecting a reflective mask onto a substrate. FIG. 5A also shows a semiconductor device 34 including a photoresist layer 15 disposed on a semiconductor substrate 10 that is identical to the semiconductor substrate 210 in FIG. 4 . FIG. 5B also shows a radiation beam 50 originating from an extreme ultraviolet (EUV) source, such as that of FIG. 4 . Radiation beam 50 is directed to a photomask 80, such as a reflective photomask, wherein reflected beam 50' The angle of incidence of the reflected beam 50' is an angle A defined relative to a line 302 perpendicular to the top surface of the semiconductor substrate 10. In some embodiments, the semiconductor substrate 10 consistent with the semiconductor substrate 210 of FIG. 4 is mounted on a stage 560, and the stage 560 is coupled to and controlled by a stage controller 565. The stage controller 565 is used to move the semiconductor device 34 and to expose different positions of the semiconductor device 34 . In some embodiments, the exposure configuration 550 of FIG. 5B is a portion of the exposure apparatus 400 of FIG. 4, as described.

FIG. 6 is an inspection system 600 for a photoresist pattern disposed on a semiconductor substrate 10 . FIG. 6 shows the semiconductor device 34 on the stage 660 and the stage 660 is coupled to and controlled by the stage controller 665 . As described with respect to FIG. 2 , after cleaning the mask at the first exposure device 212 , the mask is loaded into the exposure device 400 as reflective mask 205c. In some embodiments, the semiconductor substrate 210 in FIG. 4 is the semiconductor device 34 in FIG. 5B, and the reflective mask 205c is irradiated with the radiation beam of the radiation source 100 to project the layout pattern of the reflective mask 205c onto the semiconductor device 34. on the photoresist layer 15 to generate a photoresist pattern in the photoresist layer 15 . In some embodiments, prior to exposure, the substrate 10 including the photoresist layer 15 is baked in a post application bake (PAB) operation 104 to drive out solvent in the photoresist material and cure the photoresist layer 15 . In some embodiments, after exposure, a post-exposure bake (PEB) operation 110 is performed on photoresist layer 15 . In some embodiments, after the post-exposure bake (PEB) operation 110 , a developing operation 112 is applied to the photoresist layer 15 to generate a photoresist pattern in the photoresist layer 15 .

FIG. 6 also shows a scanning imaging device 635 that produces a focused beam 619 for scanning the top surface of the photoresist layer 15 and produces an image of the photoresist pattern at the top surface of the photoresist layer 15 . In addition, FIG. 6 shows a scanning imaging device 635 and a lens 634 generating a uniform beam 617 for imaging the top surface of the photoresist layer 15 and generating an image of the photoresist pattern on the top surface of the photoresist layer 15 . In addition, the scanning imaging device 635 is coupled to the analyzer module 630 including the image processing unit 633 to receive and process the generated image of the top surface of the photoresist layer 15 . In some embodiments, the generated image of the photoresist pattern on the top surface of the photoresist layer 15 is inspected. In some embodiments, the image processing unit 633 of the analyzer module 630 performs one or more image processing and/or image recognition algorithms on the generated image of the top surface of the photoresist layer 15 and determines the The critical dimension (CD) of the photoresist pattern produced in layer 15 is measured. In some embodiments, focused beam 619 and uniform beam 617 are light beams. In some embodiments, focused beam 619 is an electron beam. In some embodiments, as described above, the semiconductor device 34 is placed on the stage 660 and the stage controller 665 of the stage 660 moves the semiconductor device 34 relative to the scanning imaging device 635 . In some embodiments, the stage controller 665 coordinates the movement of the scanning imaging device 635 and the semiconductor device 34 placed on the stage 660, and the stage controller 665 enables the scanning imaging device 635 to be positioned at different locations on the semiconductor device 34. One or more images of the developed photoresist pattern of the photoresist layer 15 disposed on the semiconductor device 34 are captured.

In some embodiments, the analyzer module 630 or the image processing unit 633 of the analyzer module 630 also determines the critical dimension uniformity (CD uniformity, CDU) of the developed photoresist pattern of the photoresist layer 15 . Analyzer module 630 determines particle and/or hydrocarbon contamination from the surface of the reticle if the critical dimension uniformity (CDU) meets predetermined criteria, for example, if the critical dimension uniformity (CDU) is better than one percent A predetermined amount of time is sufficient, such as acceptable. However, if the critical dimension uniformity (CDU) does not meet the predetermined criteria, the analyzer module 630 determines that the predetermined amount of time for particle and/or hydrocarbon contamination to be cleaned from the surface of the reticle is insufficient, e.g., unacceptable , and should increase the scheduled amount of time. In some embodiments, the analyzer module increases the predetermined amount of time incrementally, eg, the predetermined amount of time is increased in increments of, for example, between about 2% and about 10%. After each step of increasing the predetermined amount of time, the critical dimension uniformity (CDU) is measured and if the critical dimension uniformity (CDU) meets the predetermined criteria, the predetermined amount of time is not continued to be increased and the predetermined amount of time is determined to be the critical dimension uniformity ( CDU) the amount of time that a predetermined criterion is met. In some embodiments, the predetermined amount of time depends on the details of the mask's layout pattern and whether particular shapes or features are present in the mask's layout pattern.

In some embodiments, the analyzer module 630 determines that a predetermined amount of time for particle and/or hydrocarbon contamination to be cleaned from the surface of the reticle is acceptable, however, the predetermined amount of time may be more than the time to meet the predetermined criteria . In some embodiments, the analyzer module 630 gradually reduces the predetermined amount of time, for example, the predetermined amount of time is gradually reduced by, for example, between about 2% and about 10%. After each step of reducing the predetermined amount of time, the critical dimension uniformity (CDU) is measured, and when the critical dimension uniformity (CDU) at this step does not meet the predetermined criteria, the predetermined amount of time is not continued to be reduced and the predetermined amount of time is determined to result in The amount of time before the critical dimension uniformity (CDU) does not meet the predetermined criteria is immediately reduced. In some embodiments, the determined predetermined amount of time is increased by a predetermined percentage (eg, between about 0.5% and about 1.5%) to increase reliability.

7A-7F are exposure apparatuses for measuring reflected projection light from a reflective mask according to some embodiments of the present disclosure. FIGS. 7A-7F are similar to FIG. 5 which shows radiation beam 50 illuminating reflective mask 80 . The light source 705 is consistent with the radiation source 100 in FIG. 4 , and the reflective mask 80 is consistent with the reflective mask 205c in FIG. 4 . However, in contrast to exposure apparatus 400 , where reflected beam 50 ′ is not directed to the substrate but coincides with exposure apparatus 212 , reflected beam 50 ′ is directed to photodetector system 710 to detect the projected image from reflective reticle 80 , e.g., projected layout pattern. The detected images are sent to the analyzer module 630 for analysis. Consistent with FIG. 5B, the angle of incidence of the reflected beam 50'

As shown in Figures 7A, 7B, and 7C, particles 702 are located on a surface 706 of the reticle (reticle 80 into which radiation beam 50 enters). Particles 702 may degrade the projected image during lithography and may affect critical dimension (CD) uniformity. In some embodiments, the light source 705 is an extreme ultraviolet (EUV) light source and the light source 705 irradiates the particles 702 with extreme ultraviolet (EUV) radiation to decompose the particles 702 . As shown in the progression of Figures 7A to 7B and the progression of Figures 7B to 7C, the particles 702 break down and become smaller. In some embodiments, the reticle 80 is illuminated with the radiation beam 50 and the projected image of the reticle 80 is continuously captured by the image detector system for a predetermined amount of time such that the particles 702 do not affect CD uniformity (CDU) and Critical Dimension Uniformity (CDU) Satisfy the threshold Critical Dimension Uniformity (CDU).

As shown in FIGS. 7D-7E, a contaminant layer 704 comprising hydrocarbon contaminants is deposited on a surface 706 of the reticle (reticle 80 into which the radiation beam 50 enters). The contamination layer 704 may degrade the projected image during lithography and may affect critical dimension (CD) uniformity. In some embodiments, the contamination layer 704 is irradiated with extreme ultraviolet (EUV) radiation to decompose the contamination layer 704 . As in the progression of Figures 7D to 7E, the contamination layer 704 is decomposed and thinned. In some embodiments, the reticle 80 is illuminated with the radiation beam 50 and the projected image of the reticle 80 is continuously captured by the image detector system for a predetermined amount of time such that the contamination layer 704 does not affect CD uniformity (CDU). ), and critical dimension uniformity (CDU) remains within a threshold of about 1% to 2% in the 3nm process at the 3nm semiconductor node.

In some embodiments, the projected image of reticle 80 captured by image detector system 710 is additionally scanned continuously by image detector system 710 . Scanning provides detection points of the entire projected image of the reticle 80 at different time instances. In some embodiments, the scanned projected image of the reticle 80 provides temporal variation of the entire projected image as well as spatial variation of the projected image at a particular time instance. FIG. 7F shows the temporal variation of the intensity at coordinate 732 at time coordinate 734 of a particular point in the captured projected image of reticle 80 . As shown in Figure 7F, the reflected intensity at a particular point increases with time until time T1 at which the intensity curve saturates at level S1 and does not increase further. Curve 738 represents the presence of particles or the presence of hydrocarbon contamination at a particular point, and the irradiation of the radiation beam 50 at the particular point breaks down the particles and increases the reflected light intensity. In some embodiments, time T1 is a predetermined amount of time required to clean surface 706 of reticle 80 and further irradiating reticle 80 does not improve reflected light intensity. In some embodiments, when the curve 738 is saturated within a predetermined time and the increase of the curve 738 within the predetermined time is less than a threshold value, for example, the increase of the curve 738 within 5 seconds is less than one percent, the cleaning is stopped and the time T1 is reached. . In some embodiments, time T1 is between about 50 seconds and about 100 seconds. In some embodiments, curve 738 is constructed for multiple points on the surface of reticle 80, time T1 is measured for multiple points, and final T1 is determined as the maximum value of measured times T1s.

FIG. 8 is a layout pattern of a control system 800 for cleaning a reticle and for projecting the cleaned reticle on a semiconductor substrate according to some embodiments of the present disclosure. The control system 800 includes an analyzer module 830 and a main controller 840 coupled to each other. In some embodiments, the control system 800 includes the stage controller 665 of FIG. 6, the image detector system 710 of FIG. 7A, the rapid exchange device (RED) controller 240 of FIG. The imaging device 635, and the vacuum pressure controller 406 of FIG. 4 . In some embodiments, main controller 840 controls and is coupled to stage controller 665 , image detector system 710 , rapid exchange device (RED) controller 240 , scanning imaging device 635 , and vacuum pressure controller 406 . In some embodiments, the main controller 840 is directly coupled to the scanning imaging device 635 , or the main controller 840 is coupled to the scanning imaging device 635 through the analyzer module 830 .

In some embodiments, the analyzer module 830 includes the analyzer module 630 in FIG. 6 , or the analyzer module 830 is the same as the analyzer module 630 in FIG. 6 . In some embodiments, the main controller 840 commands the scanning system 635 through the analyzer module 830 to capture an image of the photoresist pattern on the semiconductor substrate and determine (for example, measure) the CD of the photoresist pattern disposed on the semiconductor substrate Uniformity (CDU). As described above, the analyzer module 830 determines whether the surface of the reticle is cleaned based on the measured critical dimension uniformity (CDU). In some embodiments, the main controller 840 instructs the stage controller 665 to move the stage 660 to capture one or more images of the photoresist pattern disposed at different locations on the semiconductor substrate. In some embodiments, the main controller 840 commands the vacuum pressure controller 406 to maintain the vacuum environment inside the first exposure device 212 and the second exposure device 214 and to maintain the vacuum environment inside the reticle library 202 . In some embodiments, the master controller 840 commands the rapid exchange device (RED) controller 240 to clean the surface of the reticle in the first exposure unit 212, load the cleaned reticle into the second exposure unit 214, and Project the layout pattern of the photomask onto the photoresist layer of the substrate. In some embodiments, the main controller 840 commands the image detector system 710 to capture reflected images from the reticle during cleaning of the reticle and transmit the captured reflected images to the analyzer module 830 for analysis.

In some embodiments, the analyzer module 830 includes a data mining module 818 , a machine learning module 816 , and a neural network module 814 . As mentioned above, in some embodiments, the analyzer module 830 includes an image processing unit 633 , and the image processing unit 633 includes a data mining module 818 , a machine learning module 816 , and a neural network module 814 . In some embodiments, the data mining module 818, machine learning module 816, or neural network module 814 continuously scans the captured reflection images, determines data corresponding to reflected light from different locations on the reticle, and analyzes the data , and instantly determine changes in data to determine when the surface of the reticle is cleared of particulate and/or hydrocarbon contamination.

FIG. 9 is a flowchart of an example process 900 for cleaning a reticle and for projecting a layout pattern of the cleaned reticle on a semiconductor substrate, according to some embodiments of the present disclosure. Process 900 or a portion of process 900 may be performed by the system of FIG. 2 . In some embodiments, process 900 or a portion of process 900 is performed and/or controlled by computer system 1000 as described below with reference to FIGS. 10A and 10B . In some embodiments, process 900 or a portion of process 900 is performed by system 800 of FIG. 8 described above. The process 900 includes operation S910 of retrieving a mask in the mask library from the mask library and transferring the mask to a first exposure device. As shown in FIG. 2 , the robotic arm of the robotic device 206 picks up the mask from the mask library 202 . After picking up the mask, the robotic arm transfers the mask to the first exposure device 212 .

In operation S920, the surface of the reticle is cleaned by irradiating the surface of the reticle with extreme ultraviolet (EUV) radiation from an extreme ultraviolet (EUV) radiation source for a predetermined amount of time in a first exposure device. As shown in FIGS. 7A to 7C , the particles 702 on the surface of the photomask 80 are cleaned in the first exposure device 212 . As shown in FIGS. 7D and 7E , the surface of the photomask 80 is cleaned of hydrocarbon contamination 704 .

In operation S930, after cleaning, the photomask is transferred from the first exposure device to a second exposure device for lithography. As shown in FIG. 2 , after cleaning the reticle, the reticle is transferred from the first exposure unit 212 to the second exposure unit 214 . The mask is transferred by the robotic arm of the robotic device 206 . The lithography operation is performed in the second exposure device using the layout pattern of the mask.

In operation S940, the layout pattern of the photomask is projected onto the photoresist layer of the wafer in the second exposure device. As shown in FIG. 4 or FIG. 5B , the layout pattern of each reflective mask 205 c or 80 is projected onto the photoresist layer of the respective semiconductor substrate 210 or 10 .

10A-10B are apparatuses for cleaning a reticle and for projecting a layout pattern of the cleaned reticle on a semiconductor substrate according to some embodiments of the present disclosure. In some embodiments, the computer system 1000 is used to perform the functions of the modules of FIG. 8, which includes a main controller 840, an analyzer module 830 or 630, a carrier controller 665, and a rapid exchange device (RED) controller. 240 , the vacuum pressure controller 406 , and the image processing unit 633 of the analyzer module 630 . In some embodiments, the computer system 1000 is used to perform the process 900 of FIG. 9 .

FIG. 10A is a schematic diagram of a computer system performing the functions of an apparatus for cleaning a reticle and projecting a layout pattern of the cleaned reticle. All or part of the processes, methods and/or operations of the above-mentioned embodiments may be implemented using computer hardware and computer programs executed thereon. In FIG. 10A, a computer system 1000 is equipped with a computer 1001 including a compact disc read-only memory (eg, CD-ROM or DVD-ROM) drive 1005 and disk drive 1006, a keyboard 1002, a mouse 1003, and a screen display. 1004.

FIG. 10B is a schematic diagram showing the internal configuration of the computer system 1000 . In Figure 10B, in addition to the optical disc drive 1005 and the magnetic disc drive 1006, the computer 1001 also has one or more processors, for example: a micro processing unit (micro processing unit, MPU) 1011, a read only memory (read only memory (ROM) 1012 , random access memory (random access memory, RAM) 1013 , hard disk 1014 and bus 1015 . A read only memory (ROM) 1012 stores programs such as a boot up program. A random access memory (RAM) 1013 is connected to the micro processing unit (MPU) 1011, and the random access memory (RAM) 1013 temporarily stores commands of application programs and provides a temporary storage area. The hard disk 1014 stores application programs, system programs and data. A bus 1015 connects a micro processing unit (MPU) 1011, a read only memory (ROM) 1012, and the like. It should be noted that the computer 1001 may include a network card (not shown) for providing connection to a local area network (LAN).

The program for enabling the computer system 1000 to execute the functions of cleaning the mask and projecting the layout pattern of the cleaned mask in the above embodiment can be stored in the optical disc 1021 or the magnetic disk 1022 and transmitted to the hard disk 1014, the above-mentioned optical disc 1021 Or the disk 1022 is inserted into the optical disk drive 1005 or the disk drive 1006 . Alternatively, the above programs can be transmitted to the computer 1001 through a network (not shown) and stored in the hard disk 1014 . At execution time, the program is loaded into random access memory (RAM) 1013 . The above-mentioned program can be loaded from the optical disc 1021 or the magnetic disk 1022, and the above-mentioned program can also be directly loaded from the network. The above programs do not necessarily include, for example, an operating system (OS) or a third-party program to enable the computer 901 to execute the functions of the control system for cleaning the mask and projecting the layout pattern of the cleaned mask in the above embodiments. The above program may only include a command part to call the appropriate function (module) in a controlled mode and obtain the desired result.

One aspect of the present disclosure relates to a method comprising: retrieving a reticle from a reticle library; transferring the reticle to a first exposure device; irradiating the reticle with a first EUV radiation for a predetermined exposure time in the first exposure device cleaning the surface of the photomask; and after cleaning the surface of the photomask, transferring the photomask to a second exposure device for lithography. In some embodiments, the method further includes: maintaining the first exposure device, the second exposure device and the mask library in a vacuum environment. In some embodiments, the mask is retrieved from the mask library, and the mask is transferred to the first exposure device by the robot arm of the quick exchange device; the method further includes: by the robot of the quick exchange device Arm to transfer the reticle from the first exposure unit to the second exposure unit. In some embodiments, the method further includes: projecting the layout pattern of the mask onto the photoresist layer of the wafer by the second EUV radiation; and developing the photoresist layer to generate the photoresist pattern on the wafer. In some embodiments, the first EUV radiation is generated by a first EUV light source and the second EUV radiation is generated by a second EUV light source different from the first EUV light source. In some embodiments, the method further includes: imaging the surface of the wafer to generate an image of the photoresist pattern on the wafer; analyzing the image of the photoresist pattern to determine CDU of the photoresist pattern; and if If the critical dimension uniformity does not meet the threshold critical dimension uniformity, the predetermined irradiation time is increased. In some embodiments, the method further includes: repeatedly cleaning the surface of the photomask, projecting the layout pattern of the photomask onto the photoresist layer of the wafer, developing the photoresist layer, imaging the surface of the wafer, analyzing image of the photoresist pattern, and increasing the irradiation time until the CDU meets the threshold CDU; and adjusting the predetermined irradiation time to the irradiation time corresponding to the threshold CDU.

Another aspect of the present disclosure relates to a method, comprising: cleaning the surface of the reticle by irradiating the surface of the reticle with EUV radiation from a first EUV light source during the irradiation time in a first exposure device; cleaning the surface of the reticle Thereafter, transferring the reticle from the first exposure device to a second exposure device for lithography; and projecting the layout pattern of the reticle onto the wafer in the second exposure device using EUV radiation from a second EUV light source on the photoresist layer. In some embodiments, the method further includes: after projecting the layout pattern of the photomask onto the photoresist layer of the wafer, developing the photoresist layer to generate a photoresist pattern on the wafer. In some embodiments, the above-mentioned photomask is a reflective photomask, and the method further includes: cleaning the surface of the photomask by irradiating the entire surface of the photomask with an extreme ultraviolet beam at the first exposure device; focusing light onto the image detector to produce a detected reflected image; monitoring the detected reflected image during an illumination time; and when the increase in each point of the detected reflected image is below a threshold for a specified amount of time, then Stop cleaning the surface of the reticle. In some embodiments, the method further includes continuously scanning the entire surface of the reticle by continuously sampling the detected reflection images of the image detector to clean the surface of the reticle during the first exposure device A detection scan signal is generated where each detection scan signal corresponds to a position on the surface of the reticle; the detection scan signal at each position is monitored during the exposure time; and when each position is within a specified amount of time When the increase of the detection scan signal is lower than the threshold value, the cleaning of the surface of the mask is stopped. In some embodiments, the method further includes: analyzing the detection scan signal by one of a pattern recognition algorithm, a data mining algorithm, and a neural network algorithm to determine a plurality of surfaces of the reticle that need to be cleaned. Corresponding position. In some embodiments, the first EUV light source of the first exposure device produces EUV radiation at 13.5 nm. In some embodiments, the method further includes: maintaining the first exposure device and the second exposure device in a vacuum environment.

Yet another aspect of the present disclosure relates to a system including: a main controller, an analyzer module coupled to the main controller, a rapid exchange device with an extendable robot arm, a first exposure device and a second exposure device. The first exposure device includes a first photomask stage and a first extreme ultraviolet light source. The first photomask carrier is used for holding the photomask. The second exposure device includes a second mask stage, a second EUV light source, a stage and an optical system. The stage is used to hold the wafer. The main controller is used to command the first EUV light source to be turned on, the first EUV light source to be turned on to irradiate EUV radiation by the first EUV light source, and the first EUV light source to be turned on to be in the first photomask stage of the first exposure device The surface of the photomask is cleaned by irradiating the surface of the photomask with EUV radiation from the first EUV light source for a predetermined irradiation time. After cleaning the surface of the photomask, the main controller is used to command the fast exchange device to transfer the photomask from the first exposure device to the second photomask stage of the second exposure device for lithography operation by means of the extendable robot arm. After the photomask is transferred from the first exposure device to the second photomask stage of the second exposure device, the main controller is used to command the second EUV light source to be turned on, and the second EUV light source is turned on to irradiate the electrode by the second EUV light source. and the second EUV light source is turned on to project the layout of the mask onto the photoresist layer of the wafer through the optical system. In some embodiments, the system further includes a development system for developing the photoresist layer after projecting the layout of the photomask onto the photoresist layer of the wafer and for generating a photoresist pattern on the wafer. In some embodiments, the above-mentioned second exposure device further includes an imaging device installed on the stage, wherein, in response to a command from the main controller, the imaging device is used to capture the developed light on the surface of the wafer The image of the resist pattern is used to transmit the captured image to the analyzer module; wherein the analyzer module is used to determine the CD uniformity of the photoresist pattern on the wafer. In some embodiments, the system further includes a photomask library and a pressure controller. The photomask library is used to hold a plurality of photomasks. The pressure controller is coupled to the main controller. The pressure controller is used to maintain the first photomask in a vacuum environment. The pressure of the first exposure device, the second exposure device and the mask library. In some embodiments, the system further includes a mask library, wherein before irradiating the surface of the mask with EUV radiation, the main controller is configured to send a command to the fast exchange device to retrieve the mask from the mask library and to transfer The photomask is transferred to the first exposure device. In some embodiments, the first EUV light source and the second EUV light source have a wavelength of 13.5 nm.

As described in the above embodiments, the surface of the photomask is cleaned by using extreme ultraviolet (EUV) radiation to decompose the particles deposited on the surface of the photomask and to decompose the hydrocarbon layer deposited on the surface of the photomask. The particle and hydrocarbon layers on the surface of the reticle are cleaned without solvents by using extreme ultraviolet (EUV) radiation.

The features of several embodiments are outlined above, so those skilled in the art can better understand aspects of the present disclosure. Those skilled in the art should appreciate that they can easily use this disclosure as a basis to design or modify other processes and structures to achieve the same goals and/or achieve the same advantages as the embodiments described herein. . Those skilled in the art should also understand that these equivalent constructions do not depart from the spirit and scope of the present disclosure, and they can make various changes, substitutions and changes without departing from the spirit and scope of the present disclosure.

10: Semiconductor substrate 15: Photoresist layer 29: Radiation 30: Substrate 34: Semiconductor device 35: reflective layer 37,39: film 40: Overlay 45: Absorbent layer 50:Radiation Beam 50': reflected beam 55: Layout pattern 80: mask 100: radiation source 102: Photoresist Coating Operation 104: Post-apply bake (PAB) operation 105: Mask extraction operation 106: Mask loading and cleaning operations 108: Mask loading and exposure operation 110: Post Exposure Baking (PEB) Operation 112: Developing operation 150,300: Process flow 200: Rapid exchange device (RED) 202: Mask library 204: the first movable section 205: First Pivot Point 205a, 205b: optical components 205c: Reflection mask 205d, 205e: Reduced projection optics 206:Robot device 208: the second movable section 210: Target semiconductor substrate 212: The first exposure device 214: The second exposure device 240: Rapid exchange device (RED) controller 302: line 400: exposure device 406: Vacuum pressure controller 408: Pressure sensor 500: Cutaway view 550:Exposure configuration 560,660: carrier 565,665: Stage controllers 600: Check system 617: uniform beam 619:Focused Beam 630,830: Analyzer modules 633: Image processing unit 634: lens 635: Scanning imaging device 702: particles 704: Pollutant layer 705: light source 706: surface 710: Image detector system 732: Coordinates 734: time coordinates 738: curve 800: Control system 814:Neural network module 816:Machine Learning Module 818:Data Mining Module 840: main controller 900: Process 1000: computer system 1001: computer 1002: keyboard 1003: mouse 1004: screen display 1005: CD drive 1006:Disk drive 1011: Microprocessing unit 1012: ROM 1013: random access memory 1014: hard disk 1015: busbar 1021:CD 1022: Disk A: Angle S1: Horizontal S910, S920, S930, S940: Operation T1: time

Aspects of the present disclosure are best understood from the following detailed description, taken in conjunction with the accompanying drawings. Note that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or decreased for clarity of discussion. Figure 1 is a process flow for producing a photoresist pattern on a semiconductor substrate. Figure 2 shows a quick changer for transferring reticles between different locations. FIG. 3 is a process flow for producing a photoresist pattern on a semiconductor substrate according to some embodiments of the present disclosure. FIG. 4 is a schematic diagram of an exposure apparatus for producing photoresist patterns on a wafer. 5A-5B are cross-sectional views of the reflective mask structure and the projection of the reflective mask structure on the semiconductor device in the exposure apparatus. FIG. 6 is an inspection system for a photoresist pattern provided on a semiconductor substrate. 7A-7F are exposure apparatuses for measuring reflected projection light from a reflective mask according to some embodiments of the present disclosure. FIG. 8 is a layout pattern of a control system for cleaning a reticle and for projecting the cleaned reticle on a semiconductor substrate according to some embodiments of the present disclosure. 9 is a flowchart of an example process for cleaning a reticle and for projecting a layout pattern of the cleaned reticle on a semiconductor substrate, according to some embodiments of the present disclosure. 10A-10B are apparatuses for cleaning a reticle and for projecting a layout pattern of the cleaned reticle on a semiconductor substrate according to some embodiments of the present disclosure.

Domestic deposit information (please note in order of depositor, date, and number) none Overseas storage information (please note in order of storage country, institution, date, and number) none

102: Photoresist Coating Operation

104: Post-apply bake (PAB) operation

105: Mask extraction operation

108: Exposure operation

110: Post Exposure Baking (PEB) Operation

112: Developing operation

150: Process flow

Claims (20)

A method comprising: retrieving a mask from a mask library; transferring the mask to a first exposure device; cleaning a surface of the reticle by irradiating the surface of the reticle with a first EUV radiation for a predetermined exposure time in the first exposure device; and After cleaning the surface of the reticle, the reticle is transferred to a second exposure apparatus for lithography. The method as described in Claim 1, further comprising: The first exposure device, the second exposure device and the photomask library are kept in a vacuum environment. The method of claim 1, wherein the reticle is retrieved from the reticle library, and the reticle is transferred to the first exposure device by a robotic arm of a rapid exchange device; and The method further includes: transferring the mask from the first exposure device to the second exposure device by the robot arm of the quick exchange device. The method as described in Claim 1, further comprising: projecting a layout pattern of the reticle onto a photoresist layer of a wafer by a second EUV radiation; and The photoresist layer is developed to generate a photoresist pattern on the wafer. The method of claim 4, wherein the first EUV radiation is produced by a first EUV light source, and wherein the second EUV radiation is produced by a second EUV source different from the first EUV light source. produced by the light source. The method as described in claim item 4, further comprising: imaging a surface of the wafer to produce an image of the photoresist pattern on the wafer; analyzing the image of the photoresist pattern to determine a critical dimension uniformity of the photoresist pattern; and If the CDU does not satisfy a threshold CDU, the predetermined irradiation time is increased. The method as described in Claim 6, further comprising: repeatedly cleaning the surface of the photomask, projecting the layout pattern of the photomask onto the photoresist layer of the wafer, developing the photoresist layer, imaging the surface of the wafer, analyzing the photoresist the image of the pattern, and increasing an exposure time until the CDU satisfies the threshold CDU; and The predetermined irradiation time is adjusted to the irradiation time corresponding to the threshold CD uniformity. A method comprising: cleaning a surface of a reticle by irradiating a surface of a reticle with an EUV radiation of a first EUV light source for an exposure time in a first exposure device; after cleaning the surface of the reticle, transferring the reticle from the first exposure device to a second exposure device for lithography; and A layout pattern of the reticle is projected onto a photoresist layer of a wafer in the second exposure device using an EUV radiation from a second EUV light source. The method as described in Claim 8, further comprising: After projecting the layout pattern of the mask onto the photoresist layer of the wafer, the photoresist layer is developed to generate a photoresist pattern on the wafer. The method as described in Claim 8, wherein the mask is a reflective mask, and the method further includes: irradiating an entire surface of the reticle with an EUV beam at the first exposure device to clean the surface of the reticle; focusing a reflected light from the entire surface of the mask onto an image detector to generate a detected reflected image; monitor the detected reflected image during the exposure time; and Cleaning of the surface of the reticle is stopped when an increase in each point of the detected reflected image is below a threshold for a specified amount of time. The method as described in Claim 8, wherein the mask is a reflective mask, and the method further includes: continuously scanning an entire surface of the reticle by continuously sampling a detected reflected image of an image detector to generate a detection at the first exposure device during cleaning of the surface of the reticle scanning signals, wherein each detection scanning signal corresponds to a position on the surface of the reticle; monitor the detection scan signal at each of the locations during the exposure time; and Cleaning of the surface of the reticle is stopped when an increase in the detect scan signal per the position for a specified amount of time is below a threshold. The method as described in Claim 11, further comprising: The detection scan signal is analyzed by one of a pattern recognition algorithm, a data mining algorithm, and a neural network algorithm to determine a plurality of corresponding positions on the surface of the mask that need to be cleaned. The method of claim 8, wherein the first EUV light source of the first exposure device generates the EUV radiation at 13.5 nm. The method as described in Claim 8, further comprising: The first exposure device and the second exposure device are kept in a vacuum environment. A system comprising: a master controller; an analyzer module coupled to the main controller; a quick exchange device having an extendable mechanical arm; A first exposure device, comprising: a first photomask carrier for holding a photomask; and a first extreme ultraviolet light source; A second exposure device, comprising: a second photomask carrier; a second extreme ultraviolet light source; a stage for holding a wafer; and an optical system; Wherein, the main controller is used to command the first EUV light source to be turned on, the first EUV light source is turned on to irradiate an EUV radiation from the first EUV light source, and the first EUV light source is turned on to irradiating a surface of the photomask with the EUV radiation of the first EUV light source in the first photomask stage of the exposure device for a predetermined irradiation time to clean the surface of the photomask; Wherein, after cleaning the surface of the photomask, the main controller is used to command the quick exchange device to transfer the photomask from the first exposure device to the second photolithography operation by the extensible robot arm. the second mask stage of an exposure device; Wherein, after the photomask is transferred from the first exposure device to the second photomask stage of the second exposure device, the main controller is used to command the second EUV light source to turn on, and the second EUV light source to turn on An EUV radiation is irradiated by the second EUV light source, and the second EUV light source is turned on to project a layout of the mask onto a photoresist layer of a wafer through the optical system. The system as described in Claim 15, further comprising: A development system for developing the photoresist layer after projecting the layout of the mask onto the photoresist layer of the wafer and for producing a photoresist pattern on the wafer. The system according to claim 16, wherein the second exposure device further comprises: an imaging device mounted on the stage, wherein in response to a command from the main controller, the imaging device is used to capture an image of the developed photoresist pattern on the surface of the wafer and for transmitting the captured image to the analyzer module; Wherein the analyzer module is used to determine a critical dimension uniformity of the photoresist pattern on the wafer. The system as described in claim 16, further comprising: a mask library for holding a plurality of masks; and A pressure controller is coupled to the main controller, wherein the pressure controller is used to maintain a pressure of the first exposure device, the second exposure device and the photomask library under a vacuum environment. The system as described in Claim 15, further comprising: a reticle library, wherein the master controller is configured to send a command to the fast exchange device to retrieve the reticle from the reticle library and use the photomask before irradiating the surface of the reticle with the EUV radiation The mask is transferred to the first exposure unit. The system of claim 15, wherein the first EUV light source and the second EUV light source have a wavelength of 13.5 nm.

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